1. Field of the Invention
The present invention relates to a cutter device for use in resin-pelletizing.
2. Description of the Related Art
FIG. 9 illustrates a partial side cross-sectional view of a granulating apparatus using a general cutter device. Further, FIG. 10 illustrates a partial side cross-sectional view of an example of a fixed type cutter holder.
The cutter device cuts melted resin extruded from a die 100 using a rotationally driven cutter blade 101. Consequently, a pellet is obtained. A cutter holder 106 provided with a cutter blade 101 is fixed to a cutter shaft 102 with a fixing bolt 107.
It is necessary for obtaining a favorable pellet to maintain a die surface 100a and the cutter blade 101 in a parallel condition during the cutter device is operated. Thus, before the cutter device is operated, or each time when the cutter blade 101 is replaced with a new one, accuracy adjustment between the die surface 100a and the cutter shaft 102 is performed. However, it takes time to obtain target accuracy by the accuracy adjustment. Even in a case where the cutter device is operated by adjusting the accuracy therebetween to the target accuracy, the parallelism between the die surface 100a and the cutter blade 101 may be changed due to subtle change in temperature during an operation of peripheral equipment. Accordingly, sometimes, a cutting failure is caused.
Thus, in order to solve these problems, a method has been proposed, which utilizes a spherical element to provide an aligning function to the cutter holder to thereby maintain the parallelism between the die and the cutter blade during an operation of the cutter device.
FIG. 11 illustrates a side cross-sectional view of a granulating apparatus disclosed in Japanese Patent No. 2642579. The granulating apparatus disclosed in Japanese Patent No. 2642579 utilizes an elastic force of a plate spring 201 to ensure alignability of a movable portion.
On the other hand, another method has been provided, which utilizes a spherical element to provide an aligning function to the cutter holder thereby to maintain the parallelism between the die and the cutter blade even during an operation of the cutter device. FIG. 12 illustrates a related granulating apparatus disclosed in JP-A-2000-301532. FIG. 13 illustrates a related granulating apparatus disclosed in U.S. Pat. No. 5,624,688. FIGS. 14 and 15 illustrate a related granulating apparatus disclosed in JP-A-2003-326519.
The cutter devices disclosed in JP-A-2000-301532 and U.S. Pat. No. 5,624,688 use balls 210 and 310 so as to have the aligning function. Further, the cutter device disclosed in JP-A-2003-326519 uses pins 410 so as to have the aligning function. Further, JP-A-2003-326519 also discloses another example in which a rubber bush 207 is inserted into between the cutter shaft 202 and the cutter holder 206 as an elastic member, as illustrated in FIG. 15.
However, in the case of the devices disclosed in JP-A-2000-301532 and U.S. Pat. No. 5,624,688, the transmission of large torque is difficult, because the balls are used as torque transmission members. Further, in the case of the device disclosed in JP-A-2003-326519, the torque transmission members are pins (or shafts), which are more favorable than the balls and are still unsuitable for the transmission of large torque.
As described above, torque transmission portions serving as means for ensuring flexibility in the holder, to which the cutter blade is attached, utilize point contact or line contact. Thus, when the transmission of large torque is performed, breakage of the ball and deformation of the pin (or shaft) may occur. In addition, the related cutter devices described above have problems in that the life of each of these torque transmission members is short, and that the exchange frequency thereof is high. Hereinafter, the problems of the related cutter devices are described more particularly.
According to JP-A-2000-301532, the device disclosed therein is such that “a cutter holder is provided on a cutter shaft via a flexible joint that is displaceable in a shaft center direction.” However, no more particular description of a flexible mechanism of the joint is described in JP-A-2000-301532. However, according to the description of an embodiment of the device, it is clear that rotary torque is transmitted via a ball. That is, the transmission of rotary torque is performed utilizing point contact. When a large turning force is transmitted, a dent is generated in a contact surface of the ball. Thus, the generated dent prevents the ball from moving smoothly. As a result, the flexible performance is limited. Thus, the problems of generation of vibrations and impossibility of pelletization may occur. Accordingly, the structure disclosed in Japanese Patent No. 2642579 is unsuitable for transmission of large torque.
Similarly, the cutter device disclosed in U.S. Pat. No. 5,624,688 uses the balls as the torque transmission portion, as described above. Thus, the transmission of large torque cannot be achieved.
The device disclosed in JP-A-2003-326519 is constructed so that rotary torque is transmitted by the pin (cylindrical element) or a spherical element. In addition, a force which acts in a cutter shaft center direction is transmitted also by the same pin. Consequently, a burden is imposed on the pin. Further, because the rotary torque is received by the line contact between the pin and a pin hole, the device disclosed in JP-A-2003-326519 is unsuitable for transmission of a large force. Moreover, when a large force is continuingly added to this device during an operation thereof, what is called a “drooping” is generated on the pin or the pin hole. Thus, rattling is caused. Further, vibrations occur due to accuracy failure. Moreover, pelletizing performance failure and flexibility failure are caused. Furthermore, cutoff of the pin is caused. Finally, breakage of the cutter device itself may occur. Thus, even in the case of the structure disclosed in JP-A-2003-326519, it is difficult to continuingly maintain flexibility and favorably perform pelletizing while large torque is transmitted.
Thus, the related flexible holders utilizing the spherical elements do not have a structure enabling the transmission of large torque. Therefore, the related flexible holders cannot exercise functions sufficient to meet demands for realizing high-functions of the device and for increasing the size thereof.